diff --git a/support/include/nfs/export.h b/support/include/nfs/export.h
index f7a99ba..0911c9a 100644
--- a/support/include/nfs/export.h
+++ b/support/include/nfs/export.h
@@ -17,7 +17,8 @@
 #define NFSEXP_ALLSQUASH	0x0008
 #define NFSEXP_ASYNC		0x0010
 #define NFSEXP_GATHERED_WRITES	0x0020
-/* 40, 80, 100 unused */
+#define NFSEXP_PREALLOC		0x0040
+/* 80, 100 unused */
 #define NFSEXP_NOHIDE		0x0200
 #define NFSEXP_NOSUBTREECHECK	0x0400
 #define NFSEXP_NOAUTHNLM	0x0800
diff --git a/support/nfs/exports.c b/support/nfs/exports.c
index 525e5b1..16d03cc 100644
--- a/support/nfs/exports.c
+++ b/support/nfs/exports.c
@@ -111,6 +111,7 @@ getexportent(int fromkernel, int fromexports)
 		if (fromkernel) {
 			def_ee.e_flags &= ~NFSEXP_ASYNC;
 			def_ee.e_flags &= ~NFSEXP_GATHERED_WRITES;
+			def_ee.e_flags &= ~NFSEXP_PREALLOC;
 		}
 		def_ee.e_anonuid = 65534;
 		def_ee.e_anongid = 65534;
@@ -237,6 +238,7 @@ putexportent(struct exportent *ep)
 	fprintf(fp, "%ssync,", (ep->e_flags & NFSEXP_ASYNC)? "a" : "");
 	fprintf(fp, "%swdelay,", (ep->e_flags & NFSEXP_GATHERED_WRITES)?
 				"" : "no_");
+	fprintf(fp, "%sprealloc,", (ep->e_flags & NFSEXP_PREALLOC)? "" : "no_");
 	fprintf(fp, "%shide,", (ep->e_flags & NFSEXP_NOHIDE)?
 				"no" : "");
 	fprintf(fp, "%scrossmnt,", (ep->e_flags & NFSEXP_CROSSMOUNT)?
@@ -558,6 +560,10 @@ parseopts(char *cp, struct exportent *ep, int warn, int *had_subtree_opt_ptr)
 			ep->e_flags &= ~NFSEXP_NOACL;
 		else if (strcmp(opt, "no_acl") == 0)
 			ep->e_flags |= NFSEXP_NOACL;
+		else if (strcmp(opt, "prealloc") == 0)
+			ep->e_flags |= NFSEXP_PREALLOC;
+		else if (strcmp(opt, "no_prealloc") == 0)
+			ep->e_flags &= ~NFSEXP_PREALLOC;
 		else if (strncmp(opt, "anonuid=", 8) == 0) {
 			char *oe;
 			ep->e_anonuid = strtol(opt+8, &oe, 10);
diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c
index 18dfe5a..03dbdca 100644
--- a/utils/exportfs/exportfs.c
+++ b/utils/exportfs/exportfs.c
@@ -470,6 +470,8 @@ dump(int verbose)
 				c = dumpopt(c, "async");
 			if (ep->e_flags & NFSEXP_GATHERED_WRITES)
 				c = dumpopt(c, "wdelay");
+			if (ep->e_flags & NFSEXP_PREALLOC)
+				c = dumpopt(c, "prealloc");
 			if (ep->e_flags & NFSEXP_NOHIDE)
 				c = dumpopt(c, "nohide");
 			if (ep->e_flags & NFSEXP_CROSSMOUNT)